1. Field of the Invention
The invention relates generally to optical devices. In particular, the invention relates to silicon optical modulators fabricated on large core fin optical waveguide.
2. Description of the Related Art
Optical modulators are the key component in optical communication systems. Optical modulators are devices that convert electrical signals to optical signals. Usually, optical modulators are made of materials having strong electro-optic (EO) effects, i.e. optical property changes that occur in response to the applied electrical signal. Such optical property changes include optical refractive index and optical loss changes. Depending on the EO effects used for modulation, optical modulators may be electro-optic (EO) or electro-absorption (EA) modulators.
Both EO and EA modulators are widely used in optical telecommunication systems. However, traditional modulators are too expensive to be applied to data communication systems, which are much more cost-sensitive. Low-cost optical modulators are highly desirable for next generation data communication systems, especially for 100G and beyond systems.
Silicon based modulators have great potential to lower down the cost based on the following reasons: 1) the silicon wafer processes are very mature processes and very suitable for mass production; 2) silicon wafers are much cheaper and larger than traditionally used III-V wafers. To pursue higher modulation performances, i.e. modulation efficiency, modulation speed, etc., engineers tend to make optical modulators on smaller optical waveguides. However, smaller waveguides face significant difficulties when coupled with other optical components that have much larger optical apertures, which increases packaging cost. An ideal optical modulator should have a smaller core in the modulation region and a larger core in the coupling region to solve the problem. In other words, such modulators are “actively small” and “passively large” structures.